15561431 has 2 divisors, whose sum is σ = 15561432. Its totient is φ = 15561430.

The previous prime is 15561407. The next prime is 15561439. The reversal of 15561431 is 13416551.

It is a strong prime.

It is an emirp because it is prime and its reverse (13416551) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-15561431 is a prime.

It is a super-2 number, since 2×15561431² = 484316269535522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 15561431.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15561439) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7780715 + 7780716.

It is an arithmetic number, because the mean of its divisors is an integer number (7780716).

Almost surely, 2^15561431 is an apocalyptic number.

15561431 is a deficient number, since it is larger than the sum of its proper divisors (1).

15561431 is an equidigital number, since it uses as much as digits as its factorization.

15561431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1800, while the sum is 26.

The square root of 15561431 is about 3944.7979669433. The cubic root of 15561431 is about 249.6605045133.

Adding to 15561431 its reverse (13416551), we get a palindrome (28977982).

The spelling of 15561431 in words is "fifteen million, five hundred sixty-one thousand, four hundred thirty-one".